WO2020155041A1

WO2020155041A1 - Polyvinyl alcohol hydrogel having asymmetric pore size

Info

Publication number: WO2020155041A1
Application number: PCT/CN2019/074237
Authority: WO
Inventors: 范代娣; 李阳; 朱晨辉; 杨婵媛; 贾利平; 马晓轩; 严建亚
Original assignee: 西北大学
Priority date: 2019-01-31
Filing date: 2019-01-31
Publication date: 2020-08-06
Also published as: US20220145014A1

Abstract

The present invention relates to a polyvinyl alcohol hydrogel having an asymmetric pore size. The pore size of the upper surface of the polyvinyl alcohol hydrogel is 1-30 μm, the pore size of the lower surface thereof is 50-300 μm, and the pore size of the hydrogel gradually increases from the upper surface to the lower surface. The polyvinyl alcohol hydrogel in the present invention has excellent biocompatibility, and has functions of blocking bacteria, anti-adhesion, the absorption of exudate, promoting wound healing, observation in situ of wound healing process and the like.

Description

Polyvinyl alcohol hydrogel with asymmetric pore size

Technical field

The invention belongs to the field of biomedical materials, and specifically relates to a sponge-like hydrogel dressing with asymmetric pore diameter and a preparation method thereof.

Background technique

Hydrogel is a water-insoluble soft material with water retention. This material has a soft texture, can maintain a certain shape, and absorb a large amount of water.

The good water absorption of hydrogels makes it potential for wound dressing applications. However, the currently clinically used hydrogel dressings can only be used as moisturizing and isolation protective materials, and cannot meet the requirements of both absorbing exudate and absorbing fluid as a wound dressing. The clinical requirement to prevent external bacteria from infiltrating wounds.

From the structure of the hydrogel material, there is a contradiction between the function of absorbing exudate and the function of preventing bacteria, because the pore size of the hydrogel should be as large as possible to absorb the exudate, and the pore size of the hydrogel should be as large as possible to prevent bacteria. small.

In order to balance the ability of the hydrogel material to absorb liquid and prevent bacteria, the researchers constructed a double-layer structure hydrogel—a second layer of hydrogel was prepared in situ on the surface of the first layer of hydrogel, with the pore size at the junction Suddenly, the large pores in the lower layer are loose and suitable for water absorption, and the small pores in the upper layer are dense and suitable for blocking bacteria. However, the major disadvantage of the double-layer hydrogel is the weak bonding at the interface between the two layers, and it is easy to separate and fall off during use, which limits its clinical application. In addition, researchers have also tried to use chemical hydrothermal synthesis, electrospinning and other techniques to prepare heterogeneous hydrogels, but the preparation conditions are complex and difficult to control, and large-scale preparation cannot be achieved, and the residues of toxic chemical crosslinking agents are not suitable for clinical applications. Claim. Moreover, the pore size changes of the heterogeneous structure hydrogels in the prior art are all stepwise rather than gradual. It should be noted that the non-uniform structure hydrogel refers to a hydrogel with uneven pore size, which can be a single layer or a double layer.

Therefore, how to prepare a single-layer hydrogel with asymmetric pore size in a simple and easy-to-control method is a problem that must be solved when hydrogel materials are used as wound dressings.

Summary of the invention

In view of the above-mentioned problems in the prior art, the purpose of the present invention is to provide a monolayer hydrogel with asymmetric pore size and a preparation method thereof.

The invention includes:

1. A single-layer hydrogel with asymmetric pore size, the upper surface has a pore diameter of 1-30 m, preferably 5-20 m, and the lower surface has a pore diameter of 50-300 m, preferably 80-150 m.

In this specification, the lower surface of the hydrogel refers to the surface with the larger pore size when it is used as a wound dressing, and the other surface with the smaller pore size is the upper surface. The asymmetric pore size of the hydrogel means that the pore sizes of the upper and lower surfaces are different.

2. The single-layer hydrogel according to item 1, which is a spongy polyvinyl alcohol hydrogel.

3. The monolayer hydrogel according to item 1 or 2, whose pore size gradually increases from the upper surface to the lower surface. In this specification, "gradual increase" refers to the continuous increase of the pore size in the longitudinal section direction (the thickness direction of the hydrogel) from top to bottom (not a stepwise increase). For example, for any pore of the hydrogel, take any two points A and B, with point A on the top and point B on the bottom, so that the pore size of point B is larger than that of point A.

4. A method for preparing the monolayer hydrogel according to any one of items 1 to 3, which comprises the following steps:

(1) Dissolve the water-soluble tackifier and polyvinyl alcohol in water at a certain content to obtain the water-soluble tackifier aqueous solution and the polyvinyl alcohol aqueous solution respectively; the viscosity of the water-soluble tackifier is 200-10000 cP;

(2) preparing a warm mixed liquid of a certain mixing ratio of the water-soluble tackifier aqueous solution and the polyvinyl alcohol aqueous solution;

(3) dissolving polyethylene glycol powder in the warm mixed liquid at a certain content to completely dissolve it until it is clear to obtain a hydrogel preparation liquid;

(4) Pour the hydrogel preparation solution into a template and perform low-temperature freezing to obtain the monolayer hydrogel.

In this specification, a water-soluble thickener refers to a substance that can be dissolved in water and make its aqueous solution have a certain viscosity, such as: hyaluronic acid, sodium alginate, sodium carboxymethyl cellulose, chondroitin sulfate, Keratin sulfate, etc. In one embodiment of the present invention, the water-soluble tackifier aqueous solution is composed of a water-soluble tackifier and water. In one embodiment of the present invention, the aqueous polyvinyl alcohol solution consists of polyvinyl alcohol and water. In one embodiment of the present invention, the warm mixed liquid is composed of a water-soluble tackifier, polyvinyl alcohol and water. In one embodiment of the present invention, the hydrogel preparation liquid is composed of a water-soluble tackifier, polyvinyl alcohol, polyethylene glycol, and water.

5. The preparation method according to item 4, wherein the water-soluble thickener is selected from hyaluronic acid, sodium alginate, sodium carboxymethyl cellulose, chondroitin sulfate, and keratan sulfate.

6. The preparation method according to item 4, wherein the viscosity of the water-soluble tackifier is 200-10000 cP.

7. The preparation method according to item 4, wherein the content of the water-soluble thickener in the aqueous solution of the water-soluble thickener is 0.4% by weight to 3.6% by weight.

8. The preparation method according to item 4, wherein the number average molecular weight of the polyvinyl alcohol is 70,000 to 140,000.

9. The preparation method according to item 4, wherein the content of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 12-30% by weight.

10. The preparation method according to item 4, wherein the number average molecular weight of the polyethylene glycol is 600-4000.

11. The preparation method according to item 4, wherein the content of polyethylene glycol in the hydrogel preparation liquid is 4.5-12% by weight.

12. The preparation method according to item 4, wherein the temperature of the warm mixed liquid is 70-95°C.

13. The preparation method according to item 4, wherein the low-temperature freezing temperature is -14°C--24°C, and the time is 6-30 hours.

14. The preparation method according to item 4, wherein, between the step (3) and the step (4), it further comprises a step (3-1): placing the hydrogel preparation solution at room temperature for 1-200 minute.

15. The preparation method according to item 4, wherein, in the step (2), the mixing ratio of the water-soluble tackifier aqueous solution and the polyvinyl alcohol aqueous solution is 1:1-5:1.

In addition, it is surprising that the inventors also found that the above-mentioned single-layer hydrogel can also be used to prepare a double-layer hydrogel with tightly bonded upper and lower layers and seamless butt joints. This is due to the formation of the hydrogel The composition of the two forms a hydrogen bond crosslink at the junction of the two layers. The double-layer hydrogel is not easy to separate and fall off when used as a wound dressing.

Therefore, the present invention also includes:

16. A method for preparing a double-layer hydrogel, comprising the following steps:

(1) Prepare the monolayer hydrogel according to the preparation method described in any one of items 4-14;

(2) Prepare the hydrogel preparation liquid according to steps (1)-(3) of the preparation method described in any one of items 4-14;

(3) Pour the hydrogel preparation liquid of the above step (2) on the lower surface of the monolayer hydrogel prepared in the above step (1) in a normal temperature state, and then perform low-temperature freezing to obtain a double-layer hydrogel.

For example, a single-layer hydrogel with a smaller pore size can be prepared first, and then the hydrogel preparation solution used to prepare another single-layer hydrogel with a larger pore size is poured on the single-layer hydrogel with a smaller pore size. Glue on the bottom surface.

17. The preparation method according to item 16, wherein the low-temperature freezing temperature is -14°C--24°C, and the time is 6-30 hours.

The hydrogel of the present invention has excellent biocompatibility, and has the functions of blocking bacteria, preventing adhesion, absorbing exudate, promoting wound healing, and observing wound healing process in situ.

Description of the drawings

Figure 1 is a scanning electron micrograph of the monolayer hydrogel prepared in the example. Fig. 1a is a scanning electron micrograph of the lower surface aperture of a single-layer hydrogel; Fig. 1b is a scanning electron micrograph of the upper surface; Fig. 1c is a scanning electron micrograph showing a longitudinal section of the single-layer hydrogel.

Figure 2 is a scanning electron micrograph of the double-layer hydrogel prepared in the example. Fig. 2a is a scanning electron micrograph of the upper surface of the double-layer hydrogel; Fig. 2b is a scanning electron micrograph of the lower surface; Fig. 2c is a scanning electron micrograph showing the longitudinal section of the double-layer hydrogel.

Figure 3 is a photograph showing the morphology of the dry sample and the wet sample of the double-layer hydrogel prepared in the example before and after shearing. Figure 3a is the freeze-dried sample before shearing; Figure 3b is the freeze-dried sample after shearing; Figure 3c is the wet sample before shearing. Figure 3d shows the wet sample after shearing.

Specific embodiments of the invention

In this specification, if there is no special mention,% means weight percentage.

Example 1

Step 1: Dissolve sodium carboxymethyl cellulose and polyvinyl alcohol in deionized water at 2.4% and 28% respectively to obtain a uniform clear solution;

Step 2: Dissolve polyethylene glycol powder at 80°C with a 7.5% content in the 1:1 mixed solution of step one to make it clear;

Step 3: Put the mixture prepared in Step 2 at room temperature for 50 minutes, then pour it into the template, put it in the refrigerator at -20°C for cross-linking, and after freezing for 6 hours, take it out of the refrigerator to get the hydrogel. Cycle freezing 4 Times.

In step 1, the molecular weight of polyvinyl alcohol is 95,000, and the viscosity of sodium carboxymethyl cellulose is 8,000 cP.

In step two, the molecular weight of polyethylene glycol is 1500.

Example 2

Step 1: Dissolve sodium carboxymethyl cellulose and polyvinyl alcohol in deionized water at 3.2% and 18% respectively to obtain a uniform clear solution;

Step 2: Dissolve polyethylene glycol powder into the 1:1 mixed solution of step one at a content of 7.0% at 85°C to make it clear;

Step 3: Put the mixture prepared in Step 2 at room temperature for 80 minutes, then pour it into the template, put it in the refrigerator at -22°C for cross-linking, and take it out of the refrigerator after freezing for 14 hours to get the hydrogel. Cycle freezing 1 Times.

In step 1, the molecular weight of polyvinyl alcohol is 80,000, and the viscosity of sodium carboxymethyl cellulose is 5500 cP.

In step 2, the molecular weight of polyethylene glycol is 4000.

Example 3

Step 1: Dissolve sodium carboxymethyl cellulose and polyvinyl alcohol in deionized water at 1.4% and 19% respectively to obtain a uniform clear solution;

Step 2: Dissolve polyethylene glycol powder at 90°C with a content of 10% into the 2:1 mixed solution of step 1, to make it clear;

Step 3: Put the mixed solution prepared in step 2 at room temperature for 10 minutes, then pour it into the template, put it in the refrigerator at -18°C, freeze cross-linking, and take it out of the refrigerator after freezing for 20 hours to obtain the hydrogel, cycle freezing 2 Times.

In step 1, the molecular weight of polyvinyl alcohol is 100,000, and the viscosity of sodium carboxymethyl cellulose is 9300 cP.

In step 2, the molecular weight of polyethylene glycol is 3000.

Example 4

Step 1: Hyaluronic acid and polyvinyl alcohol are dissolved in deionized water at 0.8% and 22% respectively to obtain a uniform clear solution;

Step 2: Dissolve the polyethylene glycol powder into the 1:1 mixed solution of step one at a content of 10% at 85°C to make it clear;

Step 3: Put the mixed solution prepared in step 2 at room temperature for 30 minutes, then pour it into the template, put it in the refrigerator at -18°C, freeze cross-linking, and take it out of the refrigerator after freezing for 20 hours to get the hydrogel, cycle freezing 2 Times.

In step 1, the molecular weight of polyvinyl alcohol is 120,000, and the viscosity of hyaluronic acid is 1,000 cP.

In the second step, the molecular weight of polyethylene glycol is 2000.

Example 5

Step 1: Dissolve hyaluronic acid and polyvinyl alcohol in deionized water at 1.8% and 19% respectively to obtain a uniform clear solution;

Step 2: Dissolve polyethylene glycol powder at 90°C with a content of 8.5% in the 1:1 mixed solution of step 1, to make it clear;

Step 3: Put the mixture prepared in step 2 at room temperature for 20 minutes, then pour it into the template, put it in the refrigerator at -22°C for cross-linking, and take it out of the refrigerator after freezing for 18 hours to obtain the hydrogel. Cycle freezing 4 Times.

In step 1, the molecular weight of polyvinyl alcohol is 140,000, and the viscosity of hyaluronic acid is 800 cP.

In step two, the molecular weight of polyethylene glycol is 1500.

Example 6

Step 1: Dissolve hyaluronic acid and polyvinyl alcohol in deionized water at 1.0% and 24% respectively to obtain a uniform and clear solution;

Step 2: Dissolve polyethylene glycol powder at 80°C with a 7.5% content in the 2:1 mixed solution of step one to make it clear;

In step 1, the molecular weight of polyvinyl alcohol is 100,000, and the viscosity of hyaluronic acid is 600 cP.

In step 2, the molecular weight of polyethylene glycol is 4000.

Example 7

Step 1: Dissolve sodium alginate and polyvinyl alcohol in deionized water at 0.4% and 19% respectively to obtain a uniform clear solution;

Step 2: Dissolve polyethylene glycol powder into the 3:1 mixed solution of step 1 at a content of 8.0% at 90°C to make it clear;

Step 3: Put the mixture prepared in step 2 at room temperature for 40 minutes, then pour it into the template, put it in the refrigerator at -20°C for cross-linking, and take it out of the refrigerator after freezing for 22 hours to get the hydrogel. Cycle freezing 3 Times.

In step 1, the molecular weight of polyvinyl alcohol is 90,000, and the viscosity of sodium alginate is 600 cP.

In step 2, the molecular weight of polyethylene glycol is 3000.

Example 8

Step 1: Dissolve sodium alginate and polyvinyl alcohol in deionized water at 1.4% and 24% respectively to obtain a uniform clear solution;

Step 2: Dissolve polyethylene glycol powder into the 1:1 mixed solution of step one at a content of 9.0% at 85°C to make it clear;

Step 3: Put the mixture prepared in Step 2 at room temperature for 5 minutes, then pour it into the template, put it in the refrigerator at -22°C for cross-linking, and take it out of the refrigerator after freezing for 16 hours to get the hydrogel. Cycle freezing 3 Times.

In step 1, the molecular weight of polyvinyl alcohol is 100,000, and the viscosity of sodium alginate is 800 cP.

In the second step, the molecular weight of polyethylene glycol is 2000.

Example 9

Step 1: Dissolve sodium alginate and polyvinyl alcohol in deionized water at 1.0% and 20% respectively to obtain a uniform clear solution;

Step 2: Dissolve the polyethylene glycol powder into the 1:1 mixed solution of step one at a content of 10% at 80°C to make it clear;

Step 3: Put the mixed solution prepared in Step 2 at room temperature for 30 minutes, then pour it into the template, put it in the refrigerator at -18°C, freeze cross-linking, and take it out of the refrigerator after freezing for 20 hours to get the hydrogel. Cycle freezing 4 Times.

In step 1, the molecular weight of polyvinyl alcohol is 120,000, and the viscosity of sodium alginate is 400 cP.

In step two, the molecular weight of polyethylene glycol is 1500.

For the single-layer hydrogels prepared in the foregoing Examples 1-9, the pore size of the upper and lower surfaces of the freeze-dried sample was measured by scanning electron microscopy.

The type, viscosity and content of the thickener used in the above Examples 1-9, the molecular weight and content of PVA, the molecular weight and content of PEG, the temperature of the warm mixed solution, and the time the hydrogel preparation solution is placed at room temperature, The temperature and time of low-temperature freezing, and the pore size of the upper/lower surface of the prepared hydrogel are summarized in Table 1 below.

Table 1

It can be seen from observation that the mixed solution prepared in step 2 of the above examples is clear under warm conditions, but becomes turbid and white and opaque after being left to cool. This is because PEG precipitates from the solution and phase separation occurs. . Under the teaching of this specification, those skilled in the art can control the pore size of the hydrogel by adjusting the concentration, viscosity and phase separation time.

Observation shows that the transparency of the single-layer hydrogel prepared in the foregoing embodiments is good, and the wound healing can be observed in situ at any time without removing the dressing.

Example 10

Step 1: Dissolve sodium carboxymethyl cellulose and polyvinyl alcohol in deionized water at 2.4% and 22% respectively to obtain a uniform and clear solution, then dissolve polyethylene glycol powder at 5.5% in the mixed solution at 80°C , Make it dissolve until it is clear, then put the solution at room temperature for 30 minutes and pour it into the template, and freeze it in the refrigerator at -20°C for 20 hours to obtain a monolayer hydrogel;

Step 2: After dissolving sodium carboxymethyl cellulose and polyvinyl alcohol in deionized water with a content of 2.0% and 18% respectively to obtain a uniform and clear solution, dissolve polyethylene glycol powder with a content of 10.0% at 80°C into the mixed solution Dissolve it until it is clear, then put the solution at room temperature for 30 minutes and pour it on the upper hydrogel obtained in step 1 and thawed for 2 hours, and put it in the refrigerator at -20℃ for 20 hours to obtain the double-layer hydrogel .

In step 1, the molecular weight of polyvinyl alcohol is 95,000, the viscosity of sodium carboxymethyl cellulose is 7,000 cP, and the molecular weight of polyethylene glycol is 1,500.

In the second step, the molecular weight of polyvinyl alcohol is 100,000, the viscosity of sodium carboxymethyl cellulose is 7,300 cP, and the molecular weight of polyethylene glycol is 1,500.

Figure 1 is a scanning electron micrograph of the monolayer hydrogel prepared in the example. Figure 1a is a scanning electron micrograph of the lower surface of the monolayer hydrogel with a loose structure; Figure 1b is a scanning electron micrograph of the upper surface with a dense structure. Figure c shows a longitudinal cross-sectional scanning electron microscope image of a single-layer hydrogel. It can be seen that the pore size of the hydrogel gradually increases from top to bottom in the thickness direction.

Figure 2 is a scanning electron micrograph of the double-layer hydrogel prepared in the example. Figure 2a is a scanning electron microscope image of the upper surface of the double-layer hydrogel. It can be seen that the pore size is less than 20μm and the structure is dense; Figure 2b is a scanning electron microscope image of the lower surface, which shows that the pore size is about 100μm and the pore structure is loose. Therefore, the upper and lower surfaces of the double-layer hydrogel have different pore sizes. Figure 2c shows the longitudinal cross-sectional scanning electron microscope image of the double-layer hydrogel. It can be seen from the figure that the pore size of the hydrogel gradually increases from top to bottom in the thickness direction, which is different from the two-layered double-layer hydrogel. The stepped change of the aperture between the two layers realizes seamless connection between the two layers.

Figure 3 is a photograph showing the morphology of the dry sample and the wet sample of the double-layer hydrogel prepared in the example before and after shearing. It can be seen from the figure that the dry and wet samples of the hydrogel have good adhesion between the two layers before cutting, and there are no gaps. After being cut by scissors, the wet and dry samples of the hydrogel still exhibit good adhesion. , It does not fall off due to external force, therefore, the two layers of the prepared double-layer hydrogel are tightly bonded and not easy to fall off.

The present invention has been described above through specific embodiments and examples, but those skilled in the art should understand that these are not intended to limit the scope of the present invention, and the scope of the present invention should be determined by the claims.

Industrial applicability

According to the present invention, there is provided a polyvinyl alcohol hydrogel with excellent biocompatibility, anti-bacterial, anti-adhesion, absorption of exudate, promoting wound healing, and in-situ observation of wound healing progress.

Claims

A single-layer hydrogel with asymmetric pore diameter, the upper surface pore diameter is 1-30 μm, the lower surface pore diameter is 50-300 μm, and the pore diameter gradually increases from the upper surface to the lower surface.
The single-layer hydrogel according to claim 1, which is a sponge-like polyvinyl alcohol hydrogel.
A method for preparing a single-layer hydrogel according to claim 1, which comprises the following steps:

(1) The water-soluble tackifier and polyvinyl alcohol are respectively dissolved in water at a certain content to obtain the water-soluble tackifier aqueous solution and the polyvinyl alcohol aqueous solution; the viscosity of the water-soluble tackifier is 200-10000 cP; The content of the water-soluble tackifier in the aqueous solution of the water-soluble tackifier is 0.4% by weight to 3.6% by weight;

(2) preparing a warm mixed liquid of a certain mixing ratio of the water-soluble tackifier aqueous solution and the polyvinyl alcohol aqueous solution;

(3) dissolving polyethylene glycol powder in the warm mixed liquid at a certain content to completely dissolve it until it is clear to obtain a hydrogel preparation liquid;

(4) Pour the hydrogel preparation solution into a template and perform low-temperature freezing to obtain the monolayer hydrogel.
The preparation method according to claim 3, wherein the water-soluble thickener is selected from hyaluronic acid, sodium alginate, sodium carboxymethyl cellulose, chondroitin sulfate, keratan sulfate.
The preparation method according to claim 3, wherein the low temperature freezing temperature is -14°C--24°C, and the time is 6-30 hours.
The preparation method according to claim 3, wherein between the step (3) and the step (4), it further comprises a step (3-1): placing the hydrogel preparation solution at room temperature for 1-200 minutes .
A preparation method of double-layer hydrogel, which includes the following steps:

(a) Prepare the monolayer hydrogel according to the preparation method of any one of claims 3-6;

(b) Prepare the hydrogel preparation solution according to steps (1)-(3) of the preparation method of any one of claims 3-6;

(c) Pour the hydrogel preparation liquid of the above step (b) on the lower surface of the monolayer hydrogel prepared in the above step (a) in a normal temperature state, and then perform low-temperature freezing to obtain a double-layer hydrogel.
The preparation method according to claim 7, wherein the low-temperature freezing temperature is -14°C--24°C, and the time is 6-30 hours.